The CN Tower, Toronto, was the world's tallest free-standing structure until 2007, when the Burj Khalifa in Dubai, United Arab Emirates, surpassed it. However, the CN Tower remains the world's tallest tower as defined by the Council on Tall Buildings and Urban Habitat, which defines a tower as "a building in which less than 50 per cent of the construction is usable floor space." The project's architects were John Andrews, Roger Du Toit, and the Webb Zerafa Menkès Housden Partnership; the structural engineer was R.R. Nicolet.

History and Design

Built at a cost of $52 million, it is topped off by a sophisticated communications antenna for transmission of both broadcast and microwave signals. It was opened to the public on 26 June 1976. Each year the tower attracts about 2 million visitors who ride the glassed-in elevators 342 m to the skypod, which houses both wide observation decks and the world's highest revolving restaurant. The hexagonal post-tensioned concrete tower is braced by three wings to form a broad "Y" in plan at the ground. The tapering wings rise to 330 m, the concrete tower to 450 m. The tower is topped by a 100 m steel mast for a total height of 553 m.

Of the world's observation and communications towers, the CN Tower is the most elegant. In 1995 the CN Tower was designated as one of the seven wonders of the modern world by the American Society of Civil Engineers, a designation it shares with San Francisco's Golden Gate Bridge, the Chunnel beneath the English Channel, the Empire State Building and the Itaipu Dam on the Brazil/Paraguay border.

Control of the CN Tower was acquired in 1997 by Toronto-based TrizedHahn, one of North America's largest real estate companies, selected to operate and manage the tower by Canada Lands Corporation. A major refurbishment and expansion of the tower's entertainment, shopping and restaurant facilities followed, including an IMAX film theatre and meeting rooms. In 2011, in celebration of its 35th anniversary, the CN Tower opened the EdgeWalk, a ledge 1.5 m wide encircling the tower's main pod allowing visitors to circumnavigate the tower 356 m above the ground.